In limited studies it has been documented that Vitamin B12 in doses of 2000mcg taken orally daily and thereafter taken weekly, then thereafter monthly CAN be as effective as injections of 1000mcg of injectable form vitamin B12. (pubmed.gov) From this study group and others it appears that the fragile compound of Vitamin B12 is not entirely damaged in oral form. However, in comparison to the injection, it is about a 50% less potent than taking an injections. I am guessing this is good news for those of you who are needle apprehensive.
Absorption of B12 takes place in the small intestine, right before the colon, absorption requires “intrinsic factor” which is secreted by the stomach. Hydrochloric acid is also required to split the molecule. Therefore, it is thought by many that a sublingual B12 cannot be absorbed due to the lack of strength in acid in the mouth (saliva) as well as a possible missing “intrinsic factor.” It is thought that instead of the needle, go for the nasal mist B12. Otherwise known as intra-nasal. (doctoryourself.com)
Injection form of Vitamin B12 is often prescribed for many different types of issues. It is used in treatment plans for Lou Gehrigs Disease, Alzheimers, MS, Lyme Disease, ringing in the ears, sleep disorders, and heart disease. The injection form is a guaranteed way to get the most out of this large moleculed substance. There is no upper limit of dose of B12 either.
The benefits of b12 injections is that they can be taken once or twice per week, they are effective almost immediately since it does not undergo digestion, the entire dose is used by the body and depending on the type of b12 shots you buy (methyl or cyano) the cost can actually turn out cheaper than buying oral vitamins.
There are the differences options which should give enough information to make the decision. Either way, get 6-8 hours of quality sleep a night, drink plenty of water, and be consistent with your supplements. Good Luck!!